The dwarf antelopes in the genus Madoqua are known as dikdiks. Groves (2011) recognizes 12 Madoqua species, nearly all of which are confined to the Horn of Africa (M. damarensis is found in southwestern Africa). Most of these species were formerly considered subspecies of M. saltiana or M. kirkii (the other two traditionally recognized species are M. piacentinii and M. guentheri, the latter of which Groves states includes two strongly distinct subspecies that might better be treated as species). The former subspecies of M. saltiana are M. phillipsi, M. hararensis, M. swaynei, and M. lawrancei; the former subspecies of M. kirkii are M. hindei, M. cavendishi, and M. damarensis. Madoqua thomasi was formerly treated as a synonym of M. kirkii.
Dikdiks are very small antelopes with long legs and a fine soft coat. They have relatively large eyes and ears, a prominent crest, and a fur-covered nose that is enlarged into a proboscis in some species and functions as part of a cooling system (dikdik species without this well developed system may stay cool by being mainly nocturnal). The tail is vestigial, but the pale underfur can be fanned to create a striking visual signal. These are arid-adapted antelopes and Kingdon (1997) notes that the two arid regions in which they occur (Horn of Africa and southwestern Africa) have often been connected by an arid corridor in the past.
All dikdiks rely on low thickets and succulents growing on well-drained soils with little grass. If dense, tall grass becomes established, the dikdiks move away. Males scent-mark their territories, but their territories are determined largely by the movements of the female. Territories are around a third of a hectare and densities range from around 5 to 20 per km2
The dwarf antelopes in the genus Madoqua are known as dikdiks. Groves (2011) recognizes 12 Madoqua species, nearly all of which are confined to the Horn of Africa (M. damarensis is found in southwestern Africa). Most of these species were formerly considered subspecies of M. saltiana or M. kirkii (the other two traditionally recognized species are M. piacentinii and M. guentheri, the latter of which Groves states includes two strongly distinct subspecies that might better be treated as species). The former subspecies of M. saltiana are M. phillipsi, M. hararensis, M. swaynei, and M. lawrancei; the former subspecies of M. kirkii are M. hindei, M. cavendishi, and M. damarensis. Madoqua thomasi was formerly treated as a synonym of M. kirkii.
Dikdiks are very small antelopes with long legs and a fine soft coat. They have relatively large eyes and ears, a prominent crest, and a fur-covered nose that is enlarged into a proboscis in some species and functions as part of a cooling system (dikdik species without this well developed system may stay cool by being mainly nocturnal). The tail is vestigial, but the pale underfur can be fanned to create a striking visual signal. These are arid-adapted antelopes and Kingdon (1997) notes that the two arid regions in which they occur (Horn of Africa and southwestern Africa) have often been connected by an arid corridor in the past.
All dikdiks rely on low thickets and succulents growing on well-drained soils with little grass. If dense, tall grass becomes established, the dikdiks move away. Males scent-mark their territories, but their territories are determined largely by the movements the females. Territories are around a third of a hectare and population densities range from around 5 to 20 per square km. Many disturbances may elicit a discreet crouching or creeping departure, but a sudden flight tends to elicit breathy whistles from both partners in a territory, sometimes in a duet. When a pair reunites there is often face-rubbing in which the female may lick the male's preorbital glands, which secrete in response to excitement. Flight is generally brief but swift (speeds of up to 42 kph have been recorded).
The flexible well developed proboscis in some dikdik species is lined with numerous blood vessels in the mucus membrane. These are cooled by increasing the normal breathing rate from one to nearly eight breaths per second. The cooled blood returns to the heart via a sinus where hot blood going to the brain is cooled by this returning blood in a form of rete mirabile. Selective cooling via this countercurrent exchange mechanism minimizes the risk to brain function as general body temperature rises.
(Kingdon 1997)
A dik-dik is the name for any of four species of small antelope in the genus Madoqua that live in the bushlands of eastern and southern Africa.[1]
Dik-diks stand about 30–40 centimetres (12–15.5 in) at the shoulder, are 50–70 cm (19.5–27.5 in) long, weigh 3–6 kilograms (6.6–13.2 lb) and can live for up to 10 years. Dik-diks are named for the alarm calls of the females. In addition to the females' alarm call, both the male and female make a shrill, whistling sound. These calls may alert other animals to predators.
The name dik-dik comes from an onomatopoeia of the repetitive dik sound female dik-diks whistle through their long, tubular snouts when they feel threatened.[3]
Female dik-diks are somewhat larger than males. The males have horns, which are small (about 7.6 centimetres or 3 in), slanted backwards and longitudinally grooved. The hair on the crown forms an upright tuft that sometimes partially conceals the short, ribbed horns of the male. The upper body is gray-brown, while the lower parts of the body, including the legs, belly, crest, and flanks, are tan. A bare black spot below the inside corner of each eye contains a preorbital gland that produces a dark, sticky secretion. Dik-diks insert grass stems and twigs into the gland to scent-mark their territories.
Perhaps to prevent overheating, dik-diks (especially Guenther's dik-diks) have elongated snouts with bellows-like muscles through which blood is pumped. Airflow and subsequent evaporation cools this blood before it is recirculated to the body. However, this panting is only implemented in extreme conditions; dik-diks can tolerate air temperatures of up to 40 °C (104 °F).[4]
Dik-diks have special physiological adaptations to help them survive in arid environments.[5] For instance, dik-diks have a lower density of sweat glands compared to other animals such as cattle.[5] Similarly, in more arid environments, dik-diks can concentrate their urine.[5] These adaptations help dik-diks preserve body water.[5] Because of their small body size, dik-diks are predicted to have among the highest metabolic rates and highest energy requirement per kilogram of all ruminants.[6] However, dik-diks have a lower metabolic rate than would be predicted for their size as a physiological adaptation to heat and aridity.[6]
Dik-diks live in shrublands and savannas of eastern Africa. Dik-diks seek habitats with a plentiful supply of edible plants such as shrubs. Dik-diks may live in places as varied as dense forest or open plain, but they require good cover and not too much tall grass.[7] They usually live in pairs in territories of about 5 hectares (12 acres). The territories are often in low, shrubby bushes (sometimes along dry, rocky streambeds) with plenty of cover. Dik-diks, with their dusty colored coat, are able to blend in with their surroundings. Dik-diks have an established series of runways through and around the borders of their territories that are used when they feel threatened.[8]
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Dik-diks are herbivores. Their diet mainly consists of foliage, shoots, fruit and berries, but little or no grass. They receive sufficient amounts of water from their food, which makes drinking unnecessary. Like all even-toed ungulates, they digest their food with the aid of micro-organisms in their four-chambered stomachs. After initial digestion, the food is repeatedly eructated and rechewed, a process known also as rumination, or 'chewing the cud'. Dik-diks' tapering heads may help them eat the leaves between the spines on acacia trees, and feed while still keeping their head high to detect predators.[4]
Dik-diks are monogamous,[9][10] and conflicts between territorial neighbors are rare. When they occur, the males from each territory dash at each other, either stop short or make head-to-head contact, then back off for another round, with head crests erected. Males mark their territories with dung piles, and cover the females' dung with their own.[10] One suggestion for monogamy in dik-diks is that it may be an evolutionary response to predation;[11] surrounded by predators, it is dangerous to explore, looking for new partners.[12] Pairs spend about 64% of their time together. Males, but not females, will attempt to initiate extra-pair mating if an opportunity arises.[9]
Females are sexually mature at six months and males at 12 months. The female gestates for 169 to 174 days and bears a single offspring. This happens up to twice a year (at the start and finish of the rainy season). Unlike other ruminants which are born forefeet first, the dik-dik is born nose first, with its forelegs laid back alongside its body. Females weigh about 560 to 680 g (1.23 to 1.50 lb) at birth, while males weigh 725 to 795 g (1.598 to 1.753 lb). The mother lactates for six weeks, feeding her fawn for no longer than a few minutes at a time. The survival rate for young dik-diks is 50%. The young stay concealed for a time after birth, but grow quickly and reach full size by seven months. At that age, the young are forced to leave their parents' territory. The fathers run the sons off the territory and the mothers run off the daughters.[13]
Dik-diks are hunted by leopards, caracals, lions, hyenas, wild dogs and humans. Other predators include monitor lizards, cheetahs, jackals, baboons, eagles, hawks and pythons. Dik-diks' adaptations to predation include excellent eyesight, the ability to reach speeds up to 42 km/h (26 mph), and high birth rates.[8]
The four species of dik-dik are:[1]
A dik-dik is the name for any of four species of small antelope in the genus Madoqua that live in the bushlands of eastern and southern Africa.
Dik-diks stand about 30–40 centimetres (12–15.5 in) at the shoulder, are 50–70 cm (19.5–27.5 in) long, weigh 3–6 kilograms (6.6–13.2 lb) and can live for up to 10 years. Dik-diks are named for the alarm calls of the females. In addition to the females' alarm call, both the male and female make a shrill, whistling sound. These calls may alert other animals to predators.
